1. Field of the Invention
The present invention relates to a front cowl member for a vehicle, and more particularly concerns a front cowl member that is excellent in the rigidity and deformation resistant strength and has a high weight reducing effect.
2. Description of Related Art
At the vehicle body of a vehicle and so on, a part referred to as a front cowl member is disposed on the underside of a hood panel rear portion on the vehicle front side of a front glass in a manner so as to extend in the vehicle width directions.
As has been conventionally well-known, this front cowl member is arranged so as to extend substantially in a horizontal direction relative to a vehicle body and in parallel with a vehicle width direction, and its end portion is connected to a suspension tower and its vehicle body rear side is connected to the vehicle body such as a dash panel, so that this arrangement exerts a function of a trough so as to prevent water such as rain water flowing down from the vehicle upper direction from invading into an engine room. Therefore, most of the front cowl members are designed into substantially a U-letter shape or L-letter shape in the cross-sectional view, with an opening being formed in an upward direction of the vehicle, and if necessary, various functional members, such as reinforcing members and wiper pivots, are coupled thereto.
This front cowl member couples suspension towers that receive input loads from the right and left tires of the vehicle to each other; therefore, it also has a function for improving the vehicle body rigidity at the time of traveling. For this reason, this part is also required for high twisting and bending rigidity relative to loads mainly applied in the vehicle longitudinal directions, as well as for high compression rigidity and strength against compression force exerted in the vehicle width directions. Moreover, from the viewpoint of reducing the weight of the vehicle, after achieving these rigidity and strength as well as further achieving functions for satisfying protective functions for pedestrians, the light weight of the vehicle is further demanded.
Since aluminum alloys are light in comparison with steel sheets that have been conventionally used, these are expected to be applied to the frame members. However, since these have problems in that material costs are high in comparison with those of the steel sheets, with low processability, and in that their joining costs are high, the practical use of these has not been progressed so much, and there are only few application cases to the cowl member.
As shown in FIG. 8, JP 9-202265 A discloses a cowl box 20 constituted by a cowl top panel 22 made of a plate member and a cowl box member 21 installed on the rear upper portion of this member. An extrusion member made of a light alloy is used as the cowl box member 21 for supporting a front glass 26. However, there are no prior arts in which a light alloy extrusion member made of an aluminum alloy or the like is applied to a front cowl member main body that has a function as a trough. A wiper pivot is coupled to the front cowl main body. FIG. 8 is a cross-sectional view that shows the vehicle-body cowl box unit of JP 9-202265 A when its cross section is seen in the vehicle width direction.
One of the reasons for this problem is that the fracture limit of the aluminum alloy materials is lower than that of the steel sheet. In the front cowl member, a shape drastically changing portion is formed, in particular, on each of the vehicle width direction end portions in most cases, in order to prevent it from being interfered with other members, such as suspension towers or the like, and in the case of the aluminum alloy, many limitations in the angle and height of vertical walls or the radius or the like of the corners of shoulder portions are imposed in order to suppress molding failures, such as fractures, wrinkles, or the like, with the result that a problem arises in which it is difficult to properly maintain the moldability at the shape drastically changing portion.
Moreover, in recent years, in order to ensure the protective functions for pedestrians, a breaking point or the like for use in forming a weaker portion is formed on one portion of the front cowl member in some cases as disclosed in JP 4338194 B.
However, in the case of the aluminum alloy having a small local expansion, when the breaking point or the like is locally formed, a problem tends to arise in that fractures easily occur due to concentration of distortions. Moreover, even in the case where an aluminum extrusion shaped member is adopted as the front cowl member, since its plate thickness is thicker in comparison with a thin steel member as disclosed in JP 4338194 B, and since the proof stress of material is also high, the resulting problem is that the deformation resistant strength becomes higher. For this reason, another problem is raised in that only the formation of the breaking point, such as a shelf or the like, fails to ensure predetermined functions for protecting pedestrians.
On the other hand, the front cowl member is required for bending, twisting and compression rigidity relative to load inputs from the suspension tower. In order to effectively increase the rigidity and strength while maintaining the weight reducing effect, in particular, it is most effective to increase the fastening strength and rigidity of a flange portion on the part front side to be coupled to the suspension tower. For this reason, in general-use steel sheet products, a reinforcing member is joined to the flange portion on the front side and utilized in most cases. However, even if the same effects are obtained by simply replacing the member with the aluminum alloy plate, the material costs and joining costs become higher, and another problem arises in that its merit is small from the viewpoint of manufacturing processes and so on.